1. Related Patents
This application relates to co-owned U.S. Pat. Nos. 7,189,522, 7,682,801, 7,879,597, 8,507,259, and 8,603,835 all of which are hereby incorporated by reference herein in their entireties.
2. Field
The subject disclosure relates broadly to immunoassay methods and devices. More particularly, the subject disclosure relates to the detection of one or more particular ligands in a body fluid possibly containing additional related ligands.
3. State of the Art
Many types of ligand-receptor assays have been used to detect the presence of various substances, often generally called ligands, in body fluids such as blood, urine, or saliva. These assays involve antigen antibody reactions, synthetic conjugates comprising radioactive, enzymatic, fluorescent, or visually observable polystyrene or metal sol tags, and specially designed reactor chambers. In all these assays, there is a receptor, e.g., an antibody, which is specific for the selected ligand or antigen, and a means for detecting the presence, and in some cases the amount, of the ligand-receptor reaction product. Some tests are designed to make a quantitative determination, but in many circumstances all that is required is a positive/negative qualitative indication. Examples of such qualitative assays include blood typing, most types of urinalysis, pregnancy tests, and AIDS tests. For these tests, a visually observable indicator such as the presence of agglutination or a color change is preferred.
Co-owned U.S. Pat. Nos. 7,189,522, 7,682,801, 7,879,597, and 8,507,259 are directed to improved rapid detection assays utilizing a “dual path” lateral flow device. More particularly, the immunoassay device is provided with a first sorbent strip that provides a first lateral or horizontal flow path for a conjugate, and a second sorbent strip that provides a second lateral or horizontal flow path for a sample. A test site having an immobilized ligand-binding mechanism is located on or in at least one of the strips, and the strips touch each other at the test site. In use, the sample and a buffer solution are first provided to the second sorbent strip and flow over time to the test site along the second flow path (i.e., they do not immediately wet the test site). If the sample contains ligand of interest, the ligand is captured at the test site by the immobilized ligand-binding mechanism. Buffer solution provided to the first sorbent strip carries the conjugate to the test site after the sample has reached the test site. If ligand is captured at the test site, the conjugate binds to the captured ligand and provides an indication of a “positive” test result; i.e., ligand of interest was present in the sample. If ligand is not captured at the test site, the conjugate does not bind, and a “negative” test results is obtained; i.e., ligand of interest was not present in the sample. A control line that captures conjugate may be provided near the test site to confirm that the test was properly conducted. By providing separate flow paths for the sample and the conjugate, substantially higher sensitivity and selectivity are obtained relative to standard lateral flow devices and reverse-flow devices utilizing single strips.
The dual path devices have also proved to be robust in providing accurate sensitive results where the test site is provided with multiple different immobilized ligand-binding mechanisms; i.e., multiplex capabilities. For example, separate test lines in a single DPP device have been provided for separately and accurately detecting HIV-1, HIV-2, and syphilis.